Condensing zinc vapor



May 7, 1929. F. G. BREYER CONDENSING ZINC VAPOR Filed Feb. 10, 1927 2 Sheets-Sheet lNVEN TOR ATTORN EY5 y 7, 1929- 1-7 G. BREYER CONDENSING ZINC VAPOR Filed Feb. 10, 1927 2 Sheets-Sheet INVENTOR -W My 5 ATTORNFY$ Patented May 7, 1929.

UNITED STATES; PATENT OFFICE.

FRANK G. BREYER, OF PALMERTON, PENNSYLVANIA, ASSIGNOB TO THE NEW JERSEY ZINC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

CONDENSING ZHTC VAPOR.

Application filed February 10, 1927. Serial No. 167,135.

This invention relates to the condensation otzinc vapor, and has for its object the provision of an improved method of and apparatus for condensing zinc vapor.

Zinc metal or spelter, when produced by the reduction of oxidized zinc ores at high temperatures, is almost universally made at the present. time in zinc distillation or spelter furnaces having a number of relatively small retorts to the outer ends of which, small condense-rs are attached. The retorts are usually mounted at a slight inclination, usuall inclined downward from the butt or close end towards the open or outer end. The condenser is in efiect an extension or elongation of the retort, although usually mounted in a substantially horizontal position, and hence not in exact alignment with the elongated axis of the retort. The zinc vapor and other 0 gases pass in a substantially horizontal line from the retort through the condenser, and the exhaust gases escape through the open end of the condenser. The efliciency of this present customary condensing apparatus is far from satisfactory, only about 60 to 75% of the metallic zinc vapor passing out of the retort being condensed as zinc metal or spelter, the remainder being condensed as blue powder or burning at the mouth of the condenser to zinc oxide and lost.

One of the objects of the present invention is to provide a condenser capable of efiiciently condensing relatively large volumes of zinc vapor. A further object of the invention is the provision of a condenser capable of handling and efficiently condensing a substantially continuous supply of zinc vapor, delivered to the condenser in relatively large volumes from a continuously operating reducing or smelting furnace. More particularly, the invention aims to provide a condenser capable of efliciently condensing the zinc vapors produced by the methods of reduction or smeltin g described in the copending application of Earl H. Bunce and myself, Serial No.

163.902, filed January 27, 1927.

The invention is based on my observations that in condensing zinc metal from gases carrying zinc vapor the closer the temperature of the condensing chamber is maintained to the temperature which will give to the con dcnsed metal the same vapor pressure as exists in the gases to be condensed the less tendency there is for the zinc vapor to condense into non-coalescing dropletsof the nature of blue powder. However, as the temperature of the condensing chamber approximates the temperature at which the vapor pressure of the condensed metal is equal to the vapor pressure in the gases to be condensed, the percentage of zinc vapor condensed (even though all of the condensed vapor be in the form of coalescing droplets) becomes less, and the recovery of zinc from the metal-laden-gases is consequently low. I have also observed that condensation is greatly-facilitated by passing the zinc vapor at some velocity by a surface over which droplets of molten zinc are flowing, after the manner of rain when it beats on a window glass.

I have discovered that by maintaining the condensing surface at an appropriate temperature gradient from the gas entrance end to the gas exit end of the condenser, and disposing the exit end at a suificient elevation above the entrance end so as to cause the metal droplets condensed near the relatively cold exit end as they accumulate to flow (or drop) backwardly across the condensing surfacetowards the relatively hot end of the condenser, the droplets which were non-coalesc ing as they existed at the relatively cold end grow and coalesce to molten masses as they progress back towards the relatively hot end. I have also found that the disposition of the condensing surface over which this tempera .ture gradient is maintained should be such that each and every small unit volume of the metal-laden gases will fiow through a relatively long path across this condensing surface in its progress from the relatively hot end to the relativel cold end thereof. I have found that such a isposition of the condensing surface may be admirably obtained in a multiplicity of relatively long tubular passages in which there is maintained a temperature gradient appropriately decreasing from the gas entrance end towards the gas exit end. By so disposing the condens-, ing surface and maintaining the-appropri ate temperature gradient, I am able to exit the gases almost completely demetalized, and to recover substantially all (95% or more) of the zinc in the form of liquid metal and not in the form of non-coalescing droplets or particles of the nature of blue powder.

In the application of these observations and discoveries to the construction of a commersially practical condenser for zine vapor,

I have found that careful consideration must be given to and quantitative adjustments made of the following factorsz 1st, accurate temperature control of the condenser as a whole; 2nd, accurate maintenance of an appropriate temperature gradient from the gas entrance end to the gas exit end; 3rd, accurate maintenance of the absolute and differential pressure conditions within the condenser; 4th, the provision of a large amount of condensing surface over which each and every small unit volume of metal-laden gases must flow a relatively long distance; 5th, the disposition of this surface so that the condensed metal as it accumulates at the relatively cold gas exit end fiows back across this surface towardsthe relatively hot gas entrance end; and 6th, the provision of a condensing surface of such physical and chemical nature as to cause the minimum adherence of condensate and to facilitate the rapid flow of the condensed metal across it.

The improved condenser of the invention embodies the aforementioned structural factors, and at the same time is capable in operation of such regulation and control as to establish and maintain the aforementioned conditions of temperatures and pressures. In its preferred form, the condenser comprises a gas distributing and molten metal collecting chamber in communication near its top with a multiplicity of relatively long conduits or tubes of relatively small cross-sectional area. The conduits are preferably upright or vertically disposed and in their en-' tirety constitute in efiect a multi-tubular condensing tower. Carbon and particularly graphite is admirably adapted as the material for the condensing surfaces of the chamber and conduits. The number of conduits and their dimensions should be such that the total inner (condensing) surfaces of all the conduits is substantially greater, and preferably many times greater, than the inner (condensing) surface of the chamber. The distributing and co lecting chamber is provided with an inlet for the gases carrying the zinc vapor to be condensed, and with an appropriate sump for the collection of the condensed metal, as well as with appropriate means, preferably a tap-hole near the bottom of the sump, for removing the molten or liquid metal. From the distributing chamber, the gases flow through the conduits or passages of the multi-tubular tower, and in these conduits or passages a substantial proportion of the metal vapor is condensed to liquid metal and flows (or drops) backwardly towards the distributing and collecting chamber. The exhaust gases escape from the condensing apparatus through the outer or relatively cold end of the conduits or tubes, and the escape of these gases is regulable in order to regulate and control the gas pressures within the condensing chamber. The

regulation of the exhaust gases may eonveniently be effected by covering the outer end of allthe conduits or tubes with a common hood or cap having one or more regulable outlets for the controlled escape of the exhaust gases. The condenser as a whole is appropriately insulated in such manner as to conveniently regulate and control the temperature gradient in the n'iulti-tubular tower.

The desired temperature controls arerealized in the condenser of the invention by appropriate relative dispositions of heat removing media and heat insulating media, utilizing only the heat derived from the condensing gases in conjunction with those med ia. to establish and maintain the desired temperature controls. The invention in its preferred form-makes possible the complete realization of this desired ten'iperature control by heat derived solely from the condensing gases. However, it is to be understood that under certain conditions the heat derived from these gases may be supplemented by extraneous heat. The desired pressure controls are realized by utilizing the pressures available in the metal-laden gases en tering the condenser, the pressures available in consequence of the differential condensation of zinc metal and the pressures available as a consequence of the stack draft of the condenser. The resistances to the flow of gas through the condenser are so disposed as to make use of these available pressures to establish and maintain the desired conditions of gas flow and metal condensation in the condenser. Y

The aforementioned and other novel features of the invention will be better understood by reference to the accompanying drawings in which I have illustrated what I now consider to be the best mode of carrying out the invention. In these drawings Fig. 1 is a sectional elevation (on the section line 1 l of Fig. of a condenser embodying the principles of the invention,

Fig. 2 is a sectional elevation of the condenser on the section line 2-2 of Fig. 3, and Fig. 3 is a top plan View of the condenser. The condenser illustrated in the drawings comprises a gas distributin g and molten metal collecting chamber 5, lined with graphite blocks 6. The bottom or metal collecting sump of the chamber 5 is downwardly inclined (V-shaped) to a central apex where a tap-hole 7 is provided for removing molten metal as required. The chamber 5 has a gas inlet 8 on one side and above the level of the molten metal accumulatin in the sump. A cleaning hole 9 is provider. on e other side of the chamber, substantially opposite the gas inlet 8. The tap-hole 7 gas inlet 8 and cleaning hole 9 are constructed of graphite tubes accurately fitting into appropriate openings in the graphite lining of the chamber. The graphite block lining 6 of the chamber is surrounded (except in the region hardened carbon paste and the whole is enclosed in a sheet metal casing or box 11. Along the apex of the V-shaped sump, natural Sil-o-cel bricks 17 are disposed between the lining 6 and the casing 11.

A multi-tubular condensing tower 12 is mounted on top of the chamber 5 with the tubes 13 in communication with the chamber.-

In the condenser illustrated in the drawings, the tower 12 is built up of a plurality (twelve) of graphite blocks, and each graphite block has a plurality (eight in this instance) of conduits 13 bored or otherwise provided therein. The tower 12, and hence the vertical tubes or conduits 13, are substantially longer (higher) than the height of the chamber 5. In the particular condenser illustrated in the drawings, the I conduits 13 are one inch in diameter and approximately four feet'long. The conduits ('96 in all) have a total surface of approximately 100 square feet, while the surface of the chamber 5 is approximately 14 square feet.

The assembled graphite blocks (in which the conduits 13 are bored) are surrounded by a layer 1 1 of hardened carbon paste enclosed on the sides by a sheet metal casing or.frame 15. The condenser as a whole is enclosed in a sheet metal casing or box 16 appropriately spaced from the box 11 and .frame 15. The spaces between the box 16 and the lower portion of the box 11 are filled with heat insulatin g material such as naturalSil-o-cel brick 17 and above this brick, the spaces between theouter box 16 and the inner box 11 and frame 15 are filled with dust coal 18.

A sheet metal hood 19 covers the tops or gas exit ends of all the conduits 13. The lower edge or rim of the hood 19 is preferably embedded to a desired extent in the surrounding dust coal 18. The hood has a top opening 20, in which plugs 21 having central orifices of different (graduated) sizes may be inserted. The exhaust gases escape from the condenser through the orifice in the plug 21 positioned in the opening 20. By appropriate selection of these plugs, and'by changing the plugs as required, the gas pressure within the condenser can be regulated and controlled by the size of the orifice of the particular plug in operative position in the opening 20.

The clean-out opening 9 has an, inner graphite plug 22 and an outer plug 23, and the space between these plugs is preferably filled with insulating material, such-as Sil-ocel powder. Similarly, the tap hole 7 has an inner graphite plug24c carried by a rod 25 ex tending beyond an outer plug 26, of fire clay or the like.

The gaseous pressure within the condenser is determined. by a pressure responsive device 27 operatively connected to an Ellison pressure gauge 28'and a pressure recording instrument 29. The device 27 may be placed in the gas inlet 8, as shown in the'drawings, or may be located in the reducing furnace or other source of the metal-laden gases near the point of withdrawal of the gaseous products. A pressure responsive device 27' is also placed within the hood 19 and is operatively connected to a pressure gauge 28 and a recording instrument 29'.

In the operation of the condenser illus tratedin the drawings, the metal laden gases enter the condenser proper through the gas inlet 8. The distributing chamber 5, the bot-- 'tom of which constitutes the molten metal sump or well, serves to distribute the gases to the vertical multi-tubular or multi-channelled condenser, and to collect the metal dropping or running from the lower ends of the individual condenser tubes. The distributing chamber 5 is the relatively hot end of the-condenser. The gases flow vertically upwardly through the long narrow tubes or channels 13 of the vertical condensing tower, depositing on the surfaces their metal burden and" escaping from the upper ends of the tubes or channels into the common hood or cap with one or more exits of controlled size. This hood or cap with its gas exit of controllable size permits the regulation and control of the pressure within the condenser by regulating the resistance of this exit. From time to time molten metal is tapped from the metal collecting sump of the chamber 5 by removing the plugs 24 and 26.

A temperature gradient is maintainedbetween the lower or entrance ends and the upper or exit ends of the tubes or passages 13, and is largely determined by maintaining approximately the same facility for heat removal fromthe lower ends as is maintained at the upper ends. The greater amount of metal condensed at the lower ends, as compared with the upper ends, gives off much more heat at the lower ends than is given off at the upper ends, and consequently a considerably higher temperature is maintained at the lower ends than is maintained at the upper ends; thisoditference in temperature being general- 1y about 200-300 C. The upper ends are furthermore differentially cooled becausethe top surfaces of the graphite blocks radiate their heat upwardly to the relatively cool hood or cap, while at the lower end the graphof zinc in the vapor exiting from the upper or exhaust ends of the tubular tower, and I particularly prefer this temperature to be equal to, if not higher than, the temperature which will give the molten condensed metal a higher vapor pressure than exists in the gases entering the lower ends of the tubes. At such high temperatures substantial amounts of the molten metal revaporize and recondense. By this means, I tend to enrich in metal vapor the gases entering the lower ends of the tubes and consequently increase the amount of metal condensing and running down inside of the tubes, which I believe pro motes coalescence of the droplets of metal coming down from the upper or relatively cold ends of the tubes.

Since the amount of heat in the gases entering the condenser (even from so large a charge as the equivalent of 50 ordinary spelfier retorts) is only. a relatively small amount and must be dissipated over a relatively large surface area, the condensing surfaces should be encompassed in as small a total volume as possibleand the exterior ofthis volume should be carefully, accurately and adj ustably insulated. The essential temperature considerations characteristic of the invention taken in conjunction with the quantities of heat available make a multi-tubular or open cellular condensing assembly particularly advantageous. In such an assembly a relatively large amount of condensing surface can be encompassed in a relatively small volume, and by making the tube or cell walls of controlled heat conducting material, heat can be removed from these condensing surfaces at such predetermined rates as to maintain these surfaces at the proper absolute temperatures and with the proper temperature differential between the relatively hot and cold ends of the condensing tubes.

It should be here noted that in condensing substances that are liquid at atmospheric temperatures, the object is to get the heat away from the condensing surface as rapidly as possible and there is present no problem of non-coalescence of the condensed substance such as is encountered in the condensation of metal vapors. In the condensation of zinc vapor to zinc metal, the zinc vapor must not be chilled too rapidly, since otherwise nothing but non-coalescing particles, such as blue powder, will be obtained. Satisfactory and efficient condensation to liquid metal can best be obtained by slowly and progressively abstracting heat from the zinc vapor. In operating the condenser of the invention, the temperature and heat absorption of the relatively cold condensing end or zone is carefully regulated, not only to avoid loss of metal in the exiting gases, but so that the condensed met-a1, which at the relatively lower temperatures has a marked tendency to condense in non-coalescing droplets, is of such temperature that as it accumulates it will fiow (or drop) freely and rapidly back into the relatively hot condensing end or zone.

It is important that the gas pressure with-- in the condenser be accurately maintained, if the optimum conditions for metal condensation are to be realized. The absolute magnitude of this pressure will depend to some extent upon the characteristics and operating condition of the apparatus producing the metal laden gases. Since the vapor pressure of molten zinc is appreciable, even when the temperature is so low that the droplets of condensed metal tend to flow sluggishly from the relatively cold condensing zone back towards the relatively hot condensing zone, the higher the pressure that can be maintained in the condenser, the higher may be the temperature of the exhaust exit gases and the more'readily will the droplets of metal condensed at the relatively cold zone flow back to the relatively hot zone of the condenser.

The condenser of the invention possesses more particularly in the multi-tubular tower at relatively large total area of condensing surface over which the metal laden gases must flow. This is of advantage because of the fact that as the particle or droplet laden gases flow by a surface the particles or droplets have a tendency to deposit on that surface, particularly where the surface is an electrical conductor. Moreover, the condensing surface, over which the metal-laden gases must flow, in serving as an attachment medium and holding surface for the droplets of metal as they condense, further promotes deposit and coalescence, inasmuch as a mobile and active surface of zinc metal is the very best deposit medium for condensing zinc gases.

The total area of condensing surface will depend of course upon the amount of metal to be condensed in a unit of time, say-24 hours; My preferred practice at the present time is to provide approximately one square foot of condensing surface per ten pounds of metal. to be condensed per 24 hours of continuous service. As a result of my experiments and investigations, I would say that satisfactory metal condensation may be obtained with as low as one-quarter of a square foot per ten pounds of metal condensed per 24 hours. As many square feet per ten pounds of metal condensed per 24 hours may be provided as can be encompassed in an assembly possessing the thermal characteristics of the invention.

Furthermore, in the condenser of the invention, the relatively large area of condensing surface is so disposed and the pressures so maintained that the metal laden gases flow substantially uniformly ,over that surface. This is due-in large measure to the relative disposition and operating characteristics of of their length and relatively small crosssectional area. The avoidance of short-circuiting to the gas exit is one of the highly important achievements of the condenser of the invention.

A multiplicity of relatively long and nar row channels as exits from a distributing chamber have a further important advantage. If for any reason there is a tendency for much of the gases to pass out of only a portion of the channels, these channels become momentarily much hotter than those through which relatively little gas is flowing. In these hotter channelsthe resistance to gas flow becomes greater in consequence of the larger volume occupied by a unit portion of the hotter gas. These channels being hotter than before also cause less zinc to condense and consequently the volume of the gases is diminished less on this account, which further causes more resistance to the flow throu h these hotter channels'thau before. On t e other hand, in the channels where relatively little gas is momentarily tending to flow. the temperature falls relative to the hotter chan-' nels and the resistance to the flow of gas through these relatively colder channels becomes le ss. At the same time, more zinc vapor is condensed thereby decreasing the actual volume of gas passing through these relatively colder channels. These conditions act to produce a lower pressure in the rela- I tivel'y colder channels than prevails in the relatively hotter channels and consequently the normal uniform and equal flow of gases through all the channels is soon automati- .eally restored.

The vertical disposition of the larger part of the total condensino surface is of particuand less precipitate.

lar advantage in facilitating the backward flow of the condensed metal, as it accumulates, from the relatively cold condensing zone towards the relatively hot condensing zone. Moreover, the droplets of'condensed metal flow more rapidly over a verticallv disposed surface and are therefore more likely to collide and rupture their non-coalescing skins, thereby promoting'coalescence, than would be the case where the flow of these droplets across the surface was more leisurely On the other hand, for

convenience or other sufficient reasons, the

multi-tu'bular condensing tower may be placed in an inclined position. The angle of inclination should, however, be such that the metal condensing at the relatively cold end flows backward towards the relatively hot end by gravity, assisted to some extent, if necesthe deposit in these tubes or channels of some adhering material, even though the condensing surfaces be ofsuch materials as have a minimum tendency for retaining adhering deposits and the metal-laden gases be of excellent composition for metal condensation. Such adhering deposits as are retained on the surface of the tubes or channels must be rubbed or scraped oif from time to time in order to keep the tubes orchannels open and their surfaces in eflicient condensing condition. The vertical or inclined disposition of the tubes or channels facilitates the removal of the adhering deposits and the cleaning of the tubes or channels without shutting down or interrupting the operations. F urthermore, with such a disposition of the tubes or channels the adhering deposits when removed fall back through the tubes or channels into the relatively hot zone of the condenser where any metal contained in the cleanings has the opportunity of coalescing with the molten metal in the collecti-ngsump.

My preferred materials for the condensing. surface, as well as the heat conducting medium in which the surface is embedded, are carbon and graphite, and this because-the zinc condensate shows the minimum tendency to adhereto and stick up such a surface. Metal droplets depositing on such surfaces (appropriately inclined) tend to quickly, a

rapidly and precipitously run down the surface, collide with each other and coalesce. Carbon and graphite surfaces, moreover, possess the advantage overa fire-clay, silica and other iron-carrying materials that they do not swell up and disintegrate as a consequence of carbon deposition from the gases. Carbon deposition from metal-carrying gases is espethe machined graphite joints but also pre vents rapid destruction of the graphite in the event of any air leakage through the surrounding mass of heat insulating material.

Carbon tubes, for examples, may be used to constitute the tubular condensing tower, witlrcarbon paste rammed and burned in between the tubes.

The inner condensing surfaces of all of the channels should be in such thermal-relation with the outside or heat-dispersing surface of the multi-channelled assembly that heat is removed with substantially the same facility fronf all of the channels. This sub stantially uniform removal of heat from all of the channels is most readily secured by em bodying the channels in a solid mass of material of appropriate heat conductivity. The better the heat-conductivity of the material the closer the channels may be together and the more bunched an assembly of channels may be. From the standpoint of utilizing only the heat in the condensing gases to maintain the proper temperatures in the condenser, the bunching of the channels is highly desirable since with less outside or heat dispersing surface to the assembly the insulation and controlled removal of heat are made easier. The heat conductivity of carbon, more particularly hardened carbon paste or graphite, is very satisfactory for these purposes. While I now prefer to embody the multiplicity of channels in a solid mass of heat conducting materials, such as carbon, it is to be understood that the desired thermal-relation between the condensing surfaces of thechannels and the outside or heat dispersing surface of the assembly may be established in other ways.

The desired thermal relation between the condensing surfaces of the channels and the outside or heat-dispersing surface of the multi-cha'nnelled assembly may, in some cases, be promoted by appropriate graduation of the resistance of the channels to the flow of gases therethrough. Thus, the resistance to the flow of gases through the inner or central channels of the assembly may be made greater than the resistance to the flow of gases through the outer channels, as, for example, by making the outer channels of larger diameter than the inner channels, in order to compensate for the poorer removal of heat from 'the inner orcentral channels. Such a graduated-resistance of the channels to the flow of gases therethrough may also be desirable to compensate for inequalities in dis- -structural elements of the condenser.

heat-insulating material will in the constructribution of the metal-laden gases to the channels, as, for example, where the gas inlet of the distributing chamber must be located in an unfavorable position to secure uniform gas distribution to all of the channels.

The following specific example of the practice of the invention will be found helpful, it is believed, in the practical application of the principles of the invention. It is to be understood that this example is merely explanatory and in no sense restrictive of the invention.

The metal laden gases, consisting largely of carbon monoxide gas and zinc vapor, were obtained from an agglomerated charge of mixed zinciferous and carbonaceous materials reduced or smelted in an externally heated vertical retort, in accordance with the principles disclosed in the aforementioned Br'eyer and Bunoe patent application. These metal laden gases were conducted from the top of the vertical retort to the gas inlet 8 of the condenser, through appropriately insulated passages. When condensing 1000 pounds of zinc metal per 24 hours, the temperature of the gases entering the condenser was from 850 to 1000 C. The distributing chamber with its molten metal sump was main tained as closely as practicable at a temperature of 850 C. The lower ends (relatively hot zone) of the tubular condensing conduits in the multi-tubular tower were at a temperature of about 700 C. The upper ends (relatively cold zone) of the tubular condensing conduits were maintained at a temperature of about 400 to 450 C.

The temperatures within the condenser are observed andrecorded from time to time by inserting the temperature-responsive or fire end of a pyrometer down through one of the tubular conduits and determining the actual temperatures at the several established control points; namely the upper ends of the conduits, the lower ends of the conduits'and the distributing chamber. Regulation of the operating temperatures within the condenser is eifected'for the most part by varying the thickness and/or depth of heat insulating material surrounding the graphite or carbon This tion of the condenser be so proportioned and correlated with respect to the contemplated conditions of operation as to approximately establish and maintain the desired temperatures within the condenser, and in actual practice accurate control of these temperatures can be obtained by varying the depth of dust coal 18.

I prefer to maintain as high a pressure as practicable in the condenser without restrictmg too much-the exit of gases-from the re-, ducing chamber. In other words, the pressure in the condenser should not be so great as to force the gas generated in the reducing chamber to flow or to be forced out of that chamber in other ways than into the condenser itself. On a foot high vertical retort furnace, I have found the maximum desirable pressure to .be about 0.25 inches of water. \Vhen the pressure in the condenser gets much above this point. the gases will blow out of the bottom of the vertical reducing cham ber instead of flowing upwardly and over into the condenser as a consequence of the stack draft induced in the chamber by the temperatures prevailing therein. As the height of the-vertical reducing chamber is increased, the pressure that may be maintained in the condenser is proportionately higher.

I prefer to have both indicating and recording pressure gauges in operative communication with the gas inlet of the condenser. It is also my preferred practice to both indicate and record the gas pressure within the hood 19. The recording instruments may, if desired, be dispensed with, since the indicating instruments furnish sufiicient infor mation for the appropriate control of the condensing operation. Moreover, it is possible in actual practice, after the operations.

of the condenser have become standardized and calibrated to rely on only one of the pressure gauges 28 or 28.

The difference inpressure between the two gauges 28 and 28 is an indication of the con- (lensing conditions prevailing in the condenser. This difl'erence in pressure more partic-' ularly indicates the existence of any stoppage or blocking of the condensing channels. Taken in conjunction with observations of the amount of zinc, if any, showin in the exiting exhaust gases, this pressure difference indicates whether or not the condenser is being overloaded.

The condenser operator is instructed to regulate the pressure in the condenser so that the gauge 28 indicates a pressure between predetermined limits, and so that the gauge 28 indicates a predetermined lower pressure (within appropriate limits) than the gauge 28. The pressure is regulated by varying the diameter of the gas exit orilice of the plug (or plugs) 21 inserted in the opening (or openings) 20 of the hood 19. Plugs of different sized orifices are provided, and the operator changes the plugs as 'requiredduring the course of the operation in order to maintain the desired predetermined pressure within the condenser.

While I have particularly mentioned the condensation of zinc vapor, it will be understood that cadmium va or, or mixed zinc and cadmium vapors, w on the latter is in excess of the normal cadmium contentof zinc smelter gases, may be equally well condensed by the principles of the invention.

It is therefore my intention in the appended claims to include in the term zine, both calmium and mixed zinc and cadmium.

I claim:

1. A condenser for zinc vapor comprising gas distributing means, a multiplicity of relatively long and narrow condenser channels communicating with said means and so disposed that condensed metal tends to flow backwardly therethrough towards said gas distributing means, the channels having a length substantially greater than the linear height of said gas distributing means.

2. A condenser for zinc vapor comprising a gas distributing and liquid metal collecting chamber having a gas inlet, a multiplicity of tubular condenser channels communicating at one end with said chamber and so disposed that condensed metal tends to flow backwanla gas inlet, a tower having a multiplicity of vertically disposed tubular condenser channels mounted above said chamber with the lower ends of the channels in communication therewith, the gas and metal contacting surfaces of said conduits being compqsed of carbon, means cooperating with the upper ends of said channels for regulating the escape of gases therefrom, means permitting the removal of liquid metal from said sump, and heat insulating material surrounding said chamber and said tower.

4. The method of condensing zinc vapor which comprises passing the gases carrying the zinc vapor to becondensed through a multiplicity of relatively long and narrow channels so disposed that condensed metal tends to flow through said channels in a direction opposite to the flow of gases therethrough, and maintaining predetermined pressure conditions in said channels by regulating the escape of gases therefrom.

5. The method of condensing zinc vapor which comprises passing the gases carrying the zine-vapor to -be condensed through a multiplicity of relatively long and narrow channels so disposed that condensed metal tends to flow through said channels in a direction opposite to the flow of gases therethrough, maintaining throughout. the length of said channels a temperature gradient decreasing from the gas entrance ends towards the gas exit ends, and maintaining predetermined conditionsof gas pressure in said channels'by regulating the escape of gases from the gas exit ends thereof.

. which comprises supplying the gases carrying,

6. The method of condensing zinc vapor Which comprises passing the gases carrying the zinc vapor to be condensed through a condensation zone in which there is maintained a temperature gradient decreasing from the gas entrance end towards the gas exit end, and controlling'the conditions of metal condensation within said condensation zone by regulating the size of the exit for the exhaust gases escaping from the gas exit end of the condensation zone.

7. The method of operating a condenser for zinc vapor which comprises maintaining the accumulating molten zinc at such a high temperature that substantial amounts of the molten zinc revaporize and recondense thereby promoting the condensation of additional zine vapor and the fiow of condensed metal towards the collecting sump for molten zinc.

8. The method of condensing zinc vapor the zinc vapor to be condensed to a chamber from which the gases are distributed to a multiplicity of relatively long and narrow chan nels so disposed that condensed metal tends to flow through said channels towards said chamber, maintaining throughout the length of said channels a temperature gradient, decreasing from the gas entrance ends towards the gas exit ends, obtaining indications of the gas pressure in said chamber, and maintain i,712,1ss

ing a predetermined gas pressure in said chamber by regulating the size of the exit or exits for the exhaust gases escaping from the gas exit ends of said channels.

9. The method of operating a condenser for zinc vapor which comprises maintaining a predetermined gas ressure within the condenser by regulating the size of the exit for the exhaust gases escaping from the condenser in accordance with observed measurements of the actual gas pressure prevailing within the condenser.

10. The method of condensing zinc vapor which comprises passing the gases carrying the zinc vapor to be condensed to a combined gas distributing and molten zinc collecting chamber, by-passing the gases and vapor through a multiplicity, of relatively long and narrow condenser channels so disposed that condensed zinc tends to flow through said channels in a direction opposite to the flow of gases therethrough, and maintaining the accun'mlating zinc in said collecting chamber atsuch a high temperature that substantial amounts of the molten zinc revaporize.

and recondense in the condenser channels thereby promoting the condensation of additional zinc vapor and the flow of condensed zinc towards the collecting chamber.

In testimony whereof I aflix my signature.-

FRANK G. BREYER. 

